1. Field of the Invention
The present invention relates to an extrusion-forming device which is preferably used, for example, for manufacturing a formed article containing a ceramic material, and a method for manufacturing a formed article by use of the device.
2. Description of the Related Art
Heretofore, as an extrusion-forming device preferably used for manufacturing a formed article containing a ceramic material or the like, for example, an extrusion-forming device has been used which extrudes a clay through a die provided at one end of a drum while kneading, homogenizing and conveying the clay containing the ceramic material by the rotation of a screw in the drum (e.g., see Patent Document 1).
FIG. 2 is a schematic constitution diagram showing one example of the conventional extrusion-forming device. In a conventional extrusion-forming device 101, as shown in FIG. 2, a drum 7 has a structure in which a screw 4 is provided. When the clay flows into the drum 7 through a supply port 19, the screw 4 in the drum 7 imparts a large shear force to knead and homogenize the clay. Then, the clay kneaded and homogenized in the drum 7 is extruded from a die 1 through a screen 2, to manufacture a formed article corresponding to the shape of the die 1.
Moreover, examples of a structure obtained by firing such a formed article include a honeycomb structure 60 having a plurality of cells 62 partitioned by partition walls 61 shown in FIG. 11. Furthermore, examples of the use application of such a honeycomb structure include a catalyst carrier for deodorization, a filter for various filtering apparatuses, a catalyst carrier utilizing the catalytic function of a heat exchange unit, an internal combustion engine, a boiler, a chemical reaction apparatus, a fuel cell reformer or the like, and a filter for collecting fine particles in an exhaust gas.
Especially in recent years, the thinning of the partition walls in the above ceramic honeycomb structure has made further progress, thereby advancing the densification of honeycomb-like slits (hereinafter referred to as “forming grooves” sometimes) through which the formed article is extrusion-formed in the die provided in the extrusion-forming device. Moreover, the amount of the clay to be supplied is increased to improve productivity, and accordingly an extrusion pressure during the pressure-forwarding of the clay in the drum rises.
[Patent Document 1] JP-A-2008-137184
As described above, the thinning of the partition walls in the ceramic honeycomb structure has made further progress. When the formed article having such densified thin walls is prepared by using the above extrusion-forming device, a large resistance is applied to the clay passing through the screen or the die. At this time, with the rise of the extrusion pressure, the clay is accumulated in the drum. Moreover, pulsation occurs in the extrusion pressure or an extrusion speed, and consequently a problem occurs that the quality of the formed article is lowered. Furthermore, for example, in the honeycomb structure obtained by firing the formed honeycomb article having such a lowered formed article quality, a crack or a defect such as a strength decrease has occurred.
The present invention has been developed in view of the above conventional problems, and an object thereof is to provide an extrusion-forming device which can consequently prevent the quality of a formed article from being lowered owing to the accumulation of a clay in a drum with the rise of an extrusion pressure and owing to pulsation occurring in the extrusion pressure or an extrusion speed and which can efficiently manufacture, with a high productivity, a formed article having a honeycomb structure having a plurality of compact cells with thinner walls and to provide a method for manufacturing an extrusion-formed article by use of the device.